You know I've ben whining about passive detection range until I read this

[Castout]

The link is here http://www.computerharpoon.com/wiki/...le=Sonar_model

Let me quote a little, it's been stikied in the DW mod section. I thought this was worth sharing.

After reading this well it seems that DW is a better game than SC. . .in terms of passive detection range.

And an unspeakable mod actually made some of the stuffs told in the article a reality such as the impossibility of detecting diesel boats.

So I say wow thank you Sonalysts.

Sonar in Real Life

Passive Sonar
Sea state and Target Noise always causes the biggest changes to sonar predictions. Target Noise and Target Speed were always calculated as one entry = Target Self Noise. Likewise, Receiver Self Noise, Receiver Speed, and Cavitation were grouped together as = Own Ship Noise. They were combined because the separate items are directly proportional to each other.
With newer nuclear submarines at speeds below 10-12 knots you're talking about detection ranges of less than a mile. Diesel submarines can become undetectable passively because they can shut down everything that makes noise, regardless of how modern they are. A modern diesel at a 2-3 knot patrol speed is probably not detectable beyond 1000 yards passively, less in high ambient noise environments. Obviously, a lot depends on ambient noise, propagation paths, layer depth, the sensitivity and location of the passive sonar receiver, proficiency of the submarine crew and operating mode, etc. In fact, in an inshore environment (shallow water, high ambient noise, high shipping density, high wreck density), attempting to track a diesel submarine passively is virtually impossible, and extremely difficult actively, and the US Navy relies primarily on non-acoustic methods for initial detection, i.e. a periscope search using ISAR radar being the most effective. MAD in a shallow water environment is handicapped also... wrecks, bottom topography, geologic features, etc., all contribute to false MAD contacts and high magnetic noise, reducing the detection range. For that reason, passive detection range for a diesel submarine in shallow water should be Zero.
Factors limiting active sonar performance in shallow water (the littoral environment) also play a major role... active sonar frequency and power affect bottom reverberation and absorption. Bottom compositions are rated on their ability to absorb and reflect sound energy. A muddy bottom will absorb a lot of energy, whereas a rocky, gravel bottom will reflect and scatter a lot of energy. Again, wrecks will give false contacts. A good diesel sub CO can avoid active detection by going dead in the water and pointing the bow or stern towards the sonar, reducing the target strength by as much as 80 per cent and not providing any Doppler return to the sonar. Or he can bottom, in which case his target echo is masked by the bottom reverb, and if he bottoms near a wreck you've got more problems.
The big point is that the environment pays a major role in the ranges observed. A Victor III in the Norwegian Sea (relatively quiet sea and deep) at 12 knots may be detected at several miles. The same submarine in the Med (relatively shallow and very noisy) may be detected at a 1000 yards. At flank speed (27 knots), the Victor III may be detected at 20 miles direct path, 25-40 miles bottom bounce, and possibly to 3 or more CZ's (convergence zones) at 30-33 miles, 60-66 miles and 90-99 miles in the Norwegian Sea, by ship based sensors and sonobouys, and for literally thousands of miles by SOSUS. What you see here is an overlap of ranges depending on transmission path, and that is entirely normal and expected. SOSUS exploits the deep sound channel, low frequency noise propagated for thousands of miles in a duct created by the effects of pressure and temperature at those depths.
This is just the tip of the iceberg, and my intent was to point out that you can't just assign hard and fast numbers. Under the right conditions a carrier may be detected acoustically well in excess of 140 miles, or may not be identified at all until it's in visual range. Assuming the carrier is detected at 140 miles, can the operator classify it as a carrier? Maybe, maybe not. If he is operating a sophisticated narrowband acoustic processor, possibly, assuming the carrier isn't using acoustic deception. If it is a broadband system (namely an active sonar being used in a passive mode), all he knows is something is making a lot of noise on a given bearing. That, combined with other intelligence may provide another piece of the puzzle, but you can't definitively classify a target with broadband sonar. A carrier launching and recovering aircraft is a different story. The noise of the catapults hitting the water brakes every 30 seconds or so is very distinctive, can be heard for long distances, and any submarine acoustic analyst has probably been trained to recognize that sound. A more comprehensive list of variables:

......
read from the link if you're interested

[SeaQueen]

Originally Posted by Castout

Under the right conditions a carrier may be detected acoustically well in excess of 140 miles, or may not be identified at all until it's in visual range. Assuming the carrier is detected at 140 miles, can the operator classify it as a carrier? Maybe, maybe not.

This might be kinda geeky but a US carrier is quite distinct because it has more screws than any other ship. It's probably a bad example, but you're right in the sense that sonar ranges could be chosen at random and you might do as well as the one trying to nail it own to the smallest detail. So much depends on variables that might not be known at all, or if they are known it's only imprecisely.

[Blacklight]

Harpoon is definitely one of the the places to go for information like this. Heck, the tabletop miniatures game (more simulation than game) has a book of data annexes that pretty much read like a condensed set of Janes books about ships, aircraft, sensors, and weapons.

[Castout]

Originally Posted by SeaQueen

This might be kinda geeky but a US carrier is quite distinct because it has more screws than any other ship. It's probably a bad example, but you're right in the sense that sonar ranges could be chosen at random and you might do as well as the one trying to nail it own to the smallest detail. So much depends on variables that might not be known at all, or if they are known it's only imprecisely.

Judging from that article I'm surprised at how easy it is for us in DW to detect a submerged diesel boat.

The mod from Russia makes it right by making diesel very very quiet and hence very difficult to be detected passively.

[Hitman]

Yeah, I'm normally a Kilo player and its current level of noise in LWAMI/Stock forces you to go too slow or even stop completely in ambush style. But given the poor range of Kilo weapons and detection ranges, this renders you harmless in too many ocasions. I'd say that at least moving at 5 knots should be safe

[SeaQueen]

Originally Posted by Castout

The mod from Russia makes it right by making diesel very very quiet and hence very difficult to be detected passively.

It depends on too many things to say one is any more right than the other.

[SeaQueen]

Originally Posted by Hitman

Yeah, I'm normally a Kilo player and its current level of noise in LWAMI/Stock forces you to go too slow or even stop completely in ambush style. But given the poor range of Kilo weapons and detection ranges, this renders you harmless in too many ocasions.

This is not unrealistic. Contrary to a lot of people's beliefs, a kilo is NOT a super-submarine. Unless it's armed with cruise missiles, most diesel electric submarines are constrained simply by their kinematic ability to get in range of it's target. They can maneuver some, but they really aren't capable of chasing down a target like a nuke might. They have to wait for a target to come to them, and then make the correct decisions that will place them in a position to make an attack. If the target zigs at the wrong time, the attack is off and all the kilo can do is wait for another target to come along. This is why their second most important attribute is not just their silence, but that they're relatively inexpensive. In order to be effective you need a lot of them because it's unlikely the enemy would even encounter just a small number.

[Molon Labe]

Originally Posted by Hitman

Yeah, I'm normally a Kilo player and its current level of noise in LWAMI/Stock forces you to go too slow or even stop completely in ambush style. But given the poor range of Kilo weapons and detection ranges, this renders you harmless in too many ocasions. I'd say that at least moving at 5 knots should be safe

Um, you can get within attack range of skimmers at 5 knots without being detected passively... in LWAMI for sure, probably stock too, even in good acoustic conditions. The non-improved Kilo might get detected in LWAMI, but those are pretty old boats and 5 knots is on the fast end of "slow".

[Hitman]

This is not unrealistic. Contrary to a lot of people's beliefs, a kilo is NOT a super-submarine. Unless it's armed with cruise missiles, most diesel electric submarines are constrained simply by their kinematic ability to get in range of it's target. They can maneuver some, but they really aren't capable of chasing down a target like a nuke might. They have to wait for a target to come to them, and then make the correct decisions that will place them in a position to make an attack. If the target zigs at the wrong time, the attack is off and all the kilo can do is wait for another target to come alone. This is why their second most important attribute is not just their silence, but that they're relatively inexpensive. In order to be effective you need a lot of them because it's unlikely the enemy would even encounter just a small number.

I know, I know, and I apply those tactics. But I still think that a Kilo should be a bit more silent in LWAMI, I'm not pretending to be able to outmaneuvre targets or overtake them at speeds of 10+ knots, but I think that moving along at 4-5 knots should be safer than it is now. Of course, accoustic conditions can change things dramatically, but in general I have played also a lot with the 688i and I can hear Kilos moving at those 5 knots easier that I would think at first glance. Tests I have conducted with LWAMI seem to indicate however that with all stop and lying in the seabed, a 688 can go right over your conning tower and not hear you :hmm: , so it's probably a matter of rescaling a bit the curve of noise increasing with speed. But when you read those news telling how chinese diesel subs seem to get closer to exercising NATO task forces than they could first think, you have to wonder.....

Um, you can get within attack range of skimmers at 5 knots without being detected passively... in LWAMI for sure, probably stock too, even in good acoustic conditions. The non-improved Kilo might get detected in LWAMI, but those are pretty old boats and 5 knots is on the fast end of "slow".

That depends of what you consider a reasonable attack range. I have run several tests to determine the endurance of my torpedoes at different speeds, and the maximum distance I would ever try to attack a nuke is 5.5 NM (Around 10.000 metres). You can attack with the SSN-15 from greater distance, but for that you need a good solution (Specially the distance to target) and you obviously can hardly get that if you are limited to move that slow.

Being lucky and having an inspired day, I have been able to get as close as 6000 metres to an enemy submarine without being detected, but that's at a mere 2 knots.

Never mind.

EDITED TO ADD:

A good example of what I'm saying is a cold war scenario I did set up some time ago, using LWAMI 3.08. A Kilo 877 versus a 688 (Non improved) in the Barents Sea, representing the russian is out there watching for enemy submarines trying to track exiting boomers from Poljarny. I did set random start boxes and fixed a reasonable area to be able to hunt around. But no matter how slow I moved, the 688 always shot at me first, without me even having been able to hear it! The first notice I have, is a TIW report. Yeah, it's a 877, but moving around at 4 knots it should be more silent, I think, specially for a non-improved 688 (Which has not the improved towed array of the 688i IIRC).

[Molon Labe]

Well that's your problem right there--the Kilo is an ASUW weapon, and you're using it to hunt SSN's. Of course you're swimming upstream!

[PeriscopeDepth]

A US 688 should still have a massive sensor advantage over a Kilo. As ML said, the Kilo is an ASUW platform. It is not meant to hunt SSNs.

PD

[Castout]

Originally Posted by Hitman

EDITED TO ADD:

A good example of what I'm saying is a cold war scenario I did set up some time ago, using LWAMI 3.08. A Kilo 877 versus a 688 (Non improved) in the Barents Sea, representing the russian is out there watching for enemy submarines trying to track exiting boomers from Poljarny. I did set random start boxes and fixed a reasonable area to be able to hunt around. But no matter how slow I moved, the 688 always shot at me first, without me even having been able to hear it! The first notice I have, is a TIW report. Yeah, it's a 877, but moving around at 4 knots it should be more silent, I think, specially for a non-improved 688 (Which has not the improved towed array of the 688i IIRC).

I think RA should fix that(I'm not saying that LWAMI is bad). With All stop you will effectively disappear with the background noise. Playing with RA has made me to respect the value of diesel boats much much more. In fact now I HATE having to watch out for those diesel subs. Closing in even within 1 nm doesn't guarantee me of detecting them passively. At slow speds they are effectively quieter than even the Seawolf SSNs. So you can imagine their quietness.

Coordination with air platforms and or surface ASW are needed to hunt for SSK. So now I know why the British didn't find the Argentine's SSKs at all even with their carrier's ASW capability.

So when I play a scenario as a lone SSN having been assigned an area known to be patrolled by enemy diesels and I can't afford to reveal my position to enemy surface combatants in the area, I just pray that I'm not passing near them and rely on my high speed capability in the event that one launches a torp at me. I cannot possibly hope to detect any of them passively and in the event that I did that would mean they were already in the kill zone of my sub.

And when assigned to hunt for SSK in relatively shallow water I can forget finding them passively........I will glare with my active. Unless I'm willing to spend extended time to outtime the diesel boat's battery or if she's stopping, her supplies( but this is no modeled in game, I mean the supplies, because depleting batteries are modeled). Diesel boats are annoying little pric*s.....I HATE THEM.

which made me think that any diesel equipped with Shkval rocket torpedo would become a very lethal mobile mine.

[SeaQueen]

Originally Posted by Hitman

But no matter how slow I moved, the 688 always shot at me first, without me even having been able to hear it! The first notice I have, is a TIW report. Yeah, it's a 877, but moving around at 4 knots it should be more silent, I think, specially for a non-improved 688 (Which has not the improved towed array of the 688i IIRC).

I would expect that sort of behavior. The Kilo is really not intended as an ASW platform. It has an ASW capability which is to say that it can shoot back, but that's very different from saying, "my platform of choice for ASW is a kilo." Really, they designed the kilo for sitting off the coast of Norway, Petropavlosk, and the Baltic Sea in order to deter amphibious assault. Hunting subs was for nukes and other platforms.

[Castout]

Originally Posted by SeaQueen

I would expect that sort of behavior. The Kilo is really not intended as an ASW platform. It has an ASW capability which is to say that it can shoot back, but that's very different from saying, "my platform of choice for ASW is a kilo." Really, they designed the kilo for sitting off the coast of Norway, Petropavlosk, and the Baltic Sea in order to deter amphibious assault. Hunting subs was for nukes and other platforms.

Yes Seaqueen but he was not emphasizing on killing the 688 but rather his own Kilo poor acoustic performance. He expected the Kilo to be more silent. And that the 688 to be noisier than him crawling at 4 knots which is a logical expectation imo.

[Molon Labe]

Originally Posted by Castout

Yes Seaqueen but he was not emphasizing on killing the 688 but rather his own Kilo poor acoustic performance. He expected the Kilo to be more silent. And that the 688 to be noisier than him crawling at 4 knots which is a logical expectation imo.

And the Kilo is, in fact, quieter than the 688 at 4 knots in LWAMI (by about 2.5 points). The Kilo still gets detected first because it has a POS sonar.